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Video Transcript: Smallpox Vaccine Administration

Segment 6 of 8:
Response to Smallpox Vaccination

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Watch this segment of the video RealOne Player RealOne Player format (3 min 6 sec)

In this segment of the program, we will describe the response to smallpox vaccination.

Following vaccination, vaccinia virus replicates in the epidermis, resulting in the development of a lesion at the site of vaccination. Persons receiving their first dose of vaccine normally experience tenderness, redness, and swelling at the vaccination site. Primary vaccination may also be associated with fever for a few days and enlarged, tender lymph nodes in the axilla of the vaccinated arm.

A papule develops at the inoculation site 3 to 5 days after primary vaccination. About 7 days following primary vaccination, a vesicle surrounded by erythema forms at the site. This is known as a "Jennerian vesicle." The vesicle usually becomes pustular by 11 days after vaccination. Maximum erythema occurs 8 to 12 days after vaccination. The erythema then subsides, the pustule dries, and a crust develops 2 to 3 weeks after vaccination. By the end of the third week, the crust separates, leaving a permanent scar at the vaccination site.

This response to vaccination is called a major reaction. It indicates that virus replication has taken place, and that vaccination was successful. A person is considered immune with the development of a major reaction at the vaccination site. A revaccinated person often develops a skin reaction similar to that after primary vaccination, but the lesion progresses faster than after primary vaccination.

Vaccine sites should be examined for the expected vesicle or pustule on about day 7 following vaccination to confirm that the vaccination was successful.

Some people may have no response or develop erythema and redness lasting only a few days. Such responses are referred to as "equivocal."

An equivocal response may result from a person being sufficiently immune to suppress viral replication, or it may be the result of using subpotent vaccine or improper technique. Some persons may exhibit erythema and redness lasting several days, which may be the result of a hypersensitivity reaction to components of the vaccine. Such responses can be induced using vaccine that has been inactivated by heat. Because it's impossible to know which of the situations pertain, the reaction is called "equivocal" and repeat vaccination is done, preferably using vaccine from another vial when possible.

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  • Page last updated December 13, 2002
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